This invention relates to an electromechanical device which can be used as a generator, electric motor, and other types of magnetic rotating components including polyphase generators and motors, steppet motors, brushless motors and the like. Because of the design, the device is admirably suited for use where flat or "pancake" designs are used.
Many electromechanical devices have been designed heretofor with varying efficiencies and ability. When size and shape are of no concern, motors and generators which utilize electrical power can be built for almost any purpose with good success. This is particularly true when the cost of the device is not considered. Difficulties and inefficiencies occur when other criteria, such as size, shape, cost etc. are incorporated into the design.
One such example of where design requirements place a burden on the motor is disclosed in U.S. Pat. No. 4,225,798, to Barrett. In Barrett, a long thin motor is disclosed which is suitable for operating automobile window opening and closing apparatus mounted in a hollow door of the vehicle. As is taught therein, considerations of space, weight and configuration have caused conventional motor design to be inadequate, particularly if they are of the common cylindrical construction. The inadequacy of cylindrical motors is clearly taught in Barrett. Another example of disadvantages of cylindrical design, when the length of the cylinder is shortened is shown in U.S. Pat. No. 4,283,647 to Herr etal. Leakage is obviously a major problem.
To obviate the design limitations shown therein, Barrett has proposed a design which includes a structure having at least two permanent magnets and at least two field shoes. Each field shoe has an arcuate surface which forms one side of an air gap between the shoe and the armature. The field shoe has a thickness and crossectional area which varies substantially in proportion to the density of magnetic flux carried by the shoe. Also the air gap is varied by constructing the shoe in a non-concentric shape. the preferred design includes two magnets and shoes, and is reported to be a powerful motor for its given size and weight. The design requirements call for a number of shaped parts for close tolerance and cooperation during the operation of the motor.
Another electromechanical machine of a flat or "pancake" design is disclosed in U.S. Pat. No. 4,188,556, to Hahn, which teaches the use of flat stator members having a circular array of magnets arranged in a suitable manner. Nevertheless, to increase power it is necessary to increase the number of magnets, thus increasing cost, weight and construction difficulties.
Other "pancake" motors which have significant power limitations are described in U.S. Pat. No. 3,315,106, to Reyst etal. In Reynst etal, the difficulties incurred with the use of printed circuit rotor discs are set forth. Reynst etal suggests the use of laminated rotors to overcome the limitations of printed circuits. U.S. Pat. No. 3,348,086 to Monma discloses another flat motor, in which flat coils are arranged on the core in a specified manner. Another such patent, which uses permanent magnet stators, is U.S. Pat. No. 3,469,133, as does the design taught in U.S. Pat. No. 3,904,902, in U.S. Pat. No. 3,993,920 and in its related U.S. Pat. No. 4,143,288.
Nevertheless, none of the above or other patents teach that a motor or generator can be designed which optimizes the ratio of the active length of a winding turn, or which permits addition of virtual poles without resorting to addition of actual magnets to reduce the core size needed for a given performance. Accordingly it is an object of this invention to provide an electromechanical device which is of high efficiency and power with low cost and without intricate or complicated design. It is an object to create a motor/generator using only two disc magnets yet having the ability to increase the number of virtual poles.